This invention relates generally to a method for inhibiting the wear in a well casing, and more particularly, to a method for inhibiting wear during drilling operations.
It is well known in the drilling industry that in those drilling areas where deviation of the bore hole is a problem, abrasive wear may occur in a well casing from a drill string. Continuing abrasive wear may cause a hole to be formed in the casing. A hole in the casing leads to serious problems; such as key seating, mud washouts and the loss of the ability to flexibly control down hole mud weights. A further problem exists when the drill string and hole deviate sharply where the drill string leaves the casing. This sharp deviation permits the drill string to bear against the bottom end of the casing and a slot is cut into the casing shoe. As more trips in and out of the hole occur, additional wear and slotting takes place, which may lead to the tool joints of the drill pipe locking in the slot. The drill string is then prevented from being removed from the hole. A hole or slot in the casing can therefore mean the loss of time, the loss of equipment, the loss of material, the loss of the use of the hole and the substantial loss of money.
One suggested solution to casing holes involves repairing the well casing after it has been holed. This solution involves the use of cement patching and re-drilling. However, this solution is time consuming and does not work toward preventing reoccurrence of holes developing at other locations within the casing.
Another suggested solution to eliminate casing holes involves the use of a soft material, such as rubber, to prevent the abrasive wear. The soft material is used as a wear sleeve which is mounted at spaced intervals on the exterior of the drill string or within the casing, as described by A. W. Kammerer, Jr. in U.S. Pat. No. 2,758,818. Sustained contact between the drill string and casing is prevented by these wear sleeves. However, these wear sleeves cause problems by being expensive, wear out quickly and may tend to restrict circulation of the drilling mud.
Accordingly, it is the primary aim of this invention to provide a method for inhibiting the wear in a well casing, which results in savings of time, equipment, material, the continued use of the hole and money.
In accordance with the invention, a method for inhibiting the wear in a well casing is provided. The wear is inhibited by determining the depths within a bore hole of a well where a drill string may contact the well casing. The casing is then run into the bore hole with one or more hardened wear sections positioned within the casing for ultimate landing at the depths where the drill string may contact the casing.